Most people are not happy with the new look of Twitter. Yours truly included.
If the new interface has been rolled out to your account and you are not happy with it, you will be happy to learn that there is a trick that can get you back to the old version.
As this is a staged rollout, for those users who have been switched, Twitter added a cookie called rweb_optin to your browser and configured it with a data value of "side_no_out". To switch back to the old Twitter interface, you simply need to delete that cookie.
If that doesn't work for you, another option is to change your user agent while on Twitter to the one used by Internet Explorer 11.
How to switch back to the old Twitter interface
There are two methods that have worked in the past to switch back to the old Twitter layout. The first method is the easiest as it just requires you to delete a cookie, but it is not reliable and users have reported it does not work anymore.